Method for assigning wheels of a motor vehicle to the respective vehicle axle

ABSTRACT

The present invention relates to a brake holder of a floating-caliper disc brake for motor vehicles at which brake pads arranged on either side of an associated brake disc are displaceably mounted. To ensure ease of displaceability a brake pad guide spring is provided that extends between the brake holder and the brake pads. For ease of mountability of both the brake pads and the brake pad guide spring, it is arranged for that the brake pad guide spring is mountable on the brake holder in a generally radial direction and is locked at the brake holder in both radial and axial directions by means of at least one fixing clamp, and at least one spring arm is designed at the brake pad guide spring and fixes at least one brake pad under spring bias in position on the brake holder in a clearance-free manner. These provisions not only improve the mountability of a brake of this type but also the rattle-free resilient arrangement of the brake pads.

TECHNICAL FIELD

The present invention relates to a method for allocating wheels of amotor vehicle to the respective vehicle axle, said wheels including aninflation tire each, whose tire pressures are monitored by a tirepressure monitoring device including at least one transmitting module ineach wheel, and at least one receiving module arranged at or in thevehicle and one evaluation module, with each transmitting moduletransmitting tire pressure information and a wheel-specificidentification number to the receiving module, which are sent to anevaluation process in the evaluation module.

BACKGROUND OF THE INVENTION

Tire pressure monitoring devices of this type are used in particular formeasuring the tire pressure of motor vehicle wheels. A wrong tirepressure causes an unnecessarily high amount of tire wear and higherfuel consumption. Further, the tire can become damaged or suddenlydestroyed due to an increased flexing energy, especially at too low tirepressure, which may lead to serious accidents in traffic.

DE 4205911 A1 discloses a monitoring device for the inflation pressureof tires of vehicle wheels. The realization presented in thisapplication is, however, very sophisticated. One mentioned embodimentincludes an associated receiver at the vehicle for each transmitter inthe wheel, while another embodiment is based on a combinedtransmitting/receiving unit in the wheel and one or more receivingdevices at the vehicle. The individual wheels are associated with themounting positions by way of a so-called pairing process performedeither manually or automatically. The manual pairing process is verytime-consuming and labor-intense and, in the event of faulty handling,can cause a wrong allocation of the individual wheels to the mountingpositions. Fail-free allocation of the individual wheels to the mountingpositions is possible in the automatic pairing process, however, thetechnical effort needed is very extensive and, hence, costly.

Further, WO 02/072369 A1 discloses a method of determining the mountingpositions (front left wheel, rear right wheel, etc.) of the vehiclewheels. The method mentioned in this publication is based on ameasurement of the vehicle wheel temperatures, and allocation of thevehicle wheels to the respective mounting position takes place by way ofthe evaluation of the vehicle wheel temperatures in dependence onspecial detecting driving maneuvers. In this arrangement, the wheelsexhibiting the highest temperature values are allocated to the drivenaxle. This allocation is, however, not correct because the temperatureincrease of the wheels mainly depends on vehicle-specific axle loadrather than on the driven axle.

BRIEF SUMMARY OF THE INVENTION

In view of the above, an object of the invention is to provide a methodpermitting an automatic allocation of the wheels to the vehicle axles ina simple fashion by taking into consideration the vehicle-specific axleload.

According to the invention, this object is achieved by a method forallocating wheels of a motor vehicle to the respective vehicle axlewherein the tire pressure changes of the wheels are considered for theallocation, and the wheels having almost identical tire pressure changesbeing allocated to one vehicle axle by taking into account avehicle-specific axle load.

The method of the invention is based on the knowledge about thevehicle-specific axle load. Based on this vehicle-specific axle load,information is stored e.g. in the evaluation process indicating whichvehicle axle, i.e. front or rear axle, is defined as the axle subjectedto higher load under constructive aspects. The method of the inventiondetermines those wheels exhibiting the highest tire pressure changes ofall wheels. As experience shows, the highest tire pressure changes occurat the wheels subjected to maximum load, with said maximally loadedwheels being disposed on the vehicle axle subjected to maximum load. Theresult is an allocation of the maximally loaded wheels to the vehicleaxle subjected to maximum load and, when knowing about thevehicle-specific axle load, an allocation of the wheels to therespective vehicle axles, i.e. front or rear axle.

According to the invention, the vehicle-specific axle load basicallyrefers to the static and dynamic axle load distribution of therespective vehicle. The static axle load distribution describes hereinthe purely static dead weight of the respective axle, for example,caused by the mounting position of the engine or due to the loading ofthe vehicle. The dynamic axle load distribution describes e.g. theeffects of a braking operation or the influence of aerodynamic measures(spoiler) on the axle load distribution.

The tire inflation pressures of the individual wheels are preferablycompared with each other over a defined, cyclically recurrent period oftime, said period of time especially ranging from roughly 50 to roughly900 seconds.

In a favorable improvement of the method, two identification numbers ofthe wheels with the greatest tire pressure changes, compared to the tirepressure changes of all wheels, are stored in a memory.

In another advantageous embodiment of the method, the identificationnumbers with the greatest tire pressure changes obtained from asubsequent period of time are compared with the identification numbersalready stored in the memory. It is expedient that the contents of thememory is preserved, and a count of a counter is increased by one whenthe identification numbers already stored in the memory are identicalwith the identification numbers obtained from a subsequent period oftime.

According to another favorable embodiment of the method, the two wheelshaving their identification numbers stored in the memory are allocatedto the vehicle axle that is considered as being subjected to higher loadwhen a determinable threshold value of the counter's count is reached.

The determinable threshold value is preferably in the range of roughly20 to roughly 100.

It is arranged for in another favorable embodiment of the method thatinformation is stored in the evaluation module indicating which vehicleaxle is considered as the axle subjected to higher load.

Besides, it is advantageous that the transmitting module will transmittire pressure information only starting from a predefinable wheel speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic setup of a vehicle equipped with a tire pressuremonitoring device.

FIG. 2 is a flow chart for illustrating an example of the method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 represents a vehicle with four inflated wheels R1 to R4 disposedon a front axle VA and a rear axle HA. Further, each wheel R1 to R4 isequipped with a transmitting module S1 to S4. These transmitting modulesS1 to S4 include batteries feeding the transmitting modules S1 to S4with energy. Besides, so-called roller switches can be provided in thetransmitting modules S1 to S4 that allow a contact between the batteriesand the transmitting modules S1 to S4 only starting with an adjustablewheel speed. These roller switches are used to achieve a longer usefullife of the batteries because there is no permanent energy supply to thetransmitting modules. In addition, the transmitting modules S1 to S4includes measuring devices, which determine the tire inflation pressureof the individual wheels R1 to R4. Further, each transmitting module S1to S4 has an individual identification number. Said identificationnumber is transmitted along with the respective tire inflation pressureto the receiving module E. This is preferably done by way of radiotransmission. The receiving module E transmits the data received to anevaluation module A. An indication unit can be connected subsequent tothe evaluation module A, informing the vehicle operator, e.g. in adisplay, about the tire pressure of the wheels R1 to R4.

FIG. 2 shows a flow chart illustrating the function of the method. Whenthe ignition 1 is switched on and a wheel speed is reached that issufficient to close the roller switch 2, transmission 3 of the tirepressure data and the identification numbers takes place from theindividual transmitting modules S1 to S4 to the receiving module E.Receiving module E leads the data received to the evaluation process.The individual tire pressures of the wheels are compared with respect toa pressure change in a step 4 over a cyclically recurrent period oftime, preferably in the range of roughly 50 to roughly 900 seconds. Itis herein determined whether the tire pressure of an individual wheelhas changed within the period of time. This routine will not be left aslong as the tire pressure of only one single wheel changes. In case achange in pressure is no longer encountered on any of the wheels, aso-called maintaining phase 5 is detected. Said maintaining phase 5describes an almost constant driving situation such as driving at arelatively constant speed. When said maintaining phase 5 is detected, acomparison 6 of the tire pressures of the individual wheels is carriedout.

Preferably, a pressure difference between e.g. a current tire pressurevalue of a wheel and a previously sent tire pressure value of the samewheel rather than the absolute pressure of the wheels is compared. Saidpressure difference allows concluding whether a wheel is disposed at avehicle axle subjected to higher load or a vehicle axle subjected tolower load, respectively. With an axle that is subjected to higher load,hence the wheels on this axle being subjected to higher load, thetemperature of these wheels will rise due to said load. The tirepressure will also rise due to this temperature rise.

Vehicle-specific information is sent to the evaluation process, fromwhich it is apparent which axle of the respective vehicle is consideredas being subjected to higher load under constructive aspects so that thewheels subjected to higher load are allocated to the axles considered asbeing subjected to higher load under constructive aspects. Thevehicle-specific information can be stored in a memory, for example.When the pressure differences of the individual wheels are compared, theevaluation process will first of all determine whether the pressuredifferences are equal or very similar in all wheels. If this is thecase, the pressure differences will neither be stored nor evaluated, andthe evaluation process starts again in the first step 4.

When the pressure differences of the wheels differ from each other,storage 7 is executed, and the two identification numbers of the wheelsin a four-wheel vehicle having the highest pressure difference values inthe monitoring cycles are written in the memory. Alternatively, it is ofcourse also possible to write the identification numbers of the wheelshaving the lowest pressure difference values in the memory.

A comparison between the identification numbers already stored in thememory and new identification numbers determined in a following cycletakes place in a subsequent step 8. When the already storedidentification numbers are identical with the newly definedidentification numbers, the memory content is preserved in a first case9, and a count of a counter is increased by one. When the newly definedidentification numbers are not identical with the identification numbersalready stored in the memory, the memory content is overwritten with thenew identification numbers and the count of the counter lowered by onein a second case 10, said count of the counter including only positivevalues. The rise or lowering of the counter's count by one shall only bereferred to herein as a possible embodiment. It is of course alsopossible that the counter has a hysteresis, or the counter can be reset.A return to step 4 and, thus, a re-run of the evaluation process takesplace in both cases 9, 10. Polling 11 of the counter's count will takeplace subsequently. It is determined by a comparison whether thecounter's count has exceeded a predeterminable threshold value,preferably in the range of roughly 20 to roughly 100. If this is thecase, there will be an allocation 12, and the wheels R1 to R4 whoseidentification numbers are stored in the memory are allocated to theaxle that is considered as being subjected to higher load, or to theaxle that is considered as being subjected to lower load, respectively.The previously stored information indicating which axle of the vehicleunder review is considered as the axle subjected to higher load or asthe axle subjected to lower load, respectively, allows the evaluationprocess to allocate two wheels either to the front axle or to the rearaxle, and thus the other two wheels are automatically allocated to theremaining vehicle axle. The content of the memory and the count of thecounter are maintained also after the ignition is switched off. If e.g.tires are changed, and the wheels are no longer mounted on the vehicleaxle where they were originally mounted, the evaluation process willdetect this condition because the identification numbers beingtransmitted starting with the change of tires no longer correspond withthe contents of the memory. Over several periods of time, the contentsof the memory is overwritten with the currently prevailingidentification numbers and the count of the counter is respectivelyincreased by one until the threshold value is exceeded, with the resultof a new allocation of the wheels R1 to R4 to the respective axles.

1-9. (canceled)
 10. A method for allocating wheels of a motor vehicle tothe respective vehicle axle, said wheels including an inflation tireeach, whose tire pressures are monitored by a tire pressure monitoringdevice including at least one transmitting module in each wheel, and atleast one receiving module arranged at or in the vehicle and oneevaluation module, with each transmitting module transmitting tirepressure information and a wheel-specific identification number to thereceiving module, which are sent to an evaluation process in theevaluation module, wherein the tire pressure changes of the wheels areconsidered for the allocation, and the wheels having almost identicaltire pressure changes being allocated to one vehicle axle by taking intoaccount a vehicle-specific axle load.
 11. The method as claimed in claim10, wherein the tire inflation pressures of the individual wheels arecompared with each other with respect to almost constant tire pressuresof the individual wheels over a defined, cyclically recurrent period oftime.
 12. The method as claimed in claim 11, wherein the twoidentification numbers of the wheels with the greatest tire pressurechanges, compared to the tire pressure changes of all wheels, are storedin a memory.
 13. The method as claimed in claim 12, wherein theidentification numbers of the wheels with the greatest tire pressurechanges obtained from a subsequent period of time are compared with theidentification numbers already stored in the memory.
 14. The method asclaimed in claim 13, wherein the contents of the memory is preserved,and a count of a counter is increased by one when the identificationnumbers already stored in the memory are identical with theidentification numbers obtained from a subsequent period of time. 15.The method as claimed in claim 14, wherein when a determinable thresholdvalue of the counter's count is reached, the two wheels having theiridentification numbers stored in the memory are allocated to the vehicleaxle that is considered as being subjected to higher load.
 16. Themethod as claimed in claim 15, wherein the determinable threshold valueis in the range of roughly 20 to roughly
 100. 17. The method as claimedin claim 15, wherein information is stored in the evaluation moduleindicating which vehicle axle is considered as the axle subjected tohigher load.
 18. The method as claimed in claim 10, wherein thetransmitting module will transmit tire pressure information onlystarting from a predefinable wheel speed.
 19. The method as claimed inclaim 11, wherein said period of time ranging from roughly 50 to roughly900 seconds.